Update: Blizzard poster Claudiog says that the issue seems to have been resolved.For my part,I am finally back online and raiding as of 11:12 PM EST.

We have had tips of a problem some players are having logging in to WoW tonight, but I can attest to it since it is happening to me as well.I can log into any US or Oceanic server except the one I usually raid on.I was on,and about to pull the first encounter in 25 man Trial of the Crusader when I was suddenly disconnected and unable to log back into the server.Several attempts to log back in later,I found that yes,I could log on to other servers,just not Norgannon, my usual home.Attempts to flush my DNS,restart my computer, my router and my modem provided no relief.I could play anywhere,save where I have characters to play.As of 9:40 pm the problem persists.So if it is happening to you,take heart in that you are not alone.

Blizzard is aware of the issue,but currently has no ETA as to when it will be fixed.